#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <bitset>
#include <utility>
using namespace std;

#define mm(a, n) memset(a, n, sizeof a)
#define mk(a, b) make_pair(a, b)

const double eps = 1e-6;
const int INF = 0x3f3f3f3f;

typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> PII;
typedef pair<double, double> PDD;
typedef pair<LL, LL> PLL;
typedef pair<int, LL> PIL;

inline void quickread() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
}

const int N = 1e5 + 10, M = 2 * N;

int n;
double p, r;
int e[N], ne[N], h[N], idx;
int sell[N];
double res = 0;

void add(int a, int b) {
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}

void dfs(int u, double p, double r) {
    if (h[u] == -1) {
        res += p * sell[u];
        return ;
    }

    for (int i = h[u]; i != -1; i = ne[i]) 
        dfs(e[i], p * r, r);
}

inline void solution() {
    mm(h, -1);
    mm(sell, 0);
    cin >> n >> p >> r;
    for (int i = 0; i < n; i ++ ) {
        int cnt;
        cin >> cnt;
        if (!cnt) {
            cin >> sell[i];
        } else {
            while (cnt -- ) {
                int idx;
                cin >> idx;
                add(i, idx);
            }
        }
    }

    dfs(0, p, r / 100 + 1);
    printf("%.1lf\n", res);
}

int main() {
    freopen("input.txt", "r", stdin);
    quickread();
    solution();
    return 0;
}